/* Backspace the archive descriptor by one blocks worth.
If its a tape, MTIOCTOP will work. If its something else,
we try to seek on it. If we can't seek, we lose! */
/* Backspace the archive descriptor by one blocks worth.
If its a tape, MTIOCTOP will work. If its something else,
we try to seek on it. If we can't seek, we lose! */